The main goal of this proposal is to investigate the role of growth factors as mediators of stromal-epithelial interactions in bladder development and dysfunction. Our previous work has shown that bladder smooth muscle (SM) is induced from undifferentiated bladder mesenchyme by bladder epithelium. This proposal is based on the hypothesis that interactions between bladder epithelial and mesenchymal cells regulate and maintain SM cell differentiation and growth in developing and dysfunctional bladders. These cell-cell interactions are mediated by the local production and action of growth factors an other paracrine acting mediators. This hypothesis will be tested using an experimental model of urethral obstruction in which bladder SM responds by undergoing hypertrophy. We have also created an experimental model of bladder augmentation in which a grafted acellular bladder tissue matrix serves as a scaffold for the ingrowth of native bladder smooth muscle and urothelial cells. During normal bladder development and in two experimental systems, cellular signaling mechanisms regulating both normal and abnormal growth and differentiation of bladder SM will be examined through pursuit of the following specific aims. (Specific aim "1) Role of growth factors as mediators of cell-cell interactions in normal bladder development and during bladder round repair. Expression of growth factors (TGF-alpha, EGF, KGF, and TGFbeta1, beta2 and beta3) and growth factor receptors will be defined in normal bladder development and during bladder wound repair by RNase protection and localized by in-situ hybridization and immunohistochemistry. (Specific aim #2) Role of growth factors and cell- cell signaling in pathogenesis of bladder hypertrophy resulting from partial obstruction of the bladder. This specific aim will be pursued by defining growth factor and growth factor receptor expression following partial bladder obstruction in rats. The hypothesis of this specific aim is that SM cells are direct targets of the physical signal eliciting fibromuscular hypertrophy and that diffusible growth factors. (TGFalpha, EGF, KGF, TGFbeta1, beta2 and beta3) are involved. To accomplish this specific aim chimeric bladders will be surgically created by grafting whole embryonic bladders or strips of neonatal or adult bladders (epithelium intact or removed) into the sub-detrusor space of adult bladders. This unique experimental design will allow study of SM development and hypertrophy in bladders from transgenic mice in which growth factor genes have been deleted or impaired (TGFalpha knockout, EGF receptor knockout, TGFbeta1 knockout and FGFR2 dominant negative (Keratin 14 promoter) mice). (Specific aim #3) Use of an acellular bladder matrix patch to study normal and abnormal development of the bladder. The strategy of this specific aim is to characterize detrusor neo-formation and fibromuscular hypertrophy following grafting of acellular bladder matrix. Additional studies will assess regional and temporal differences in growth factor expression during bladder regeneration in bladders grafted with acellular bladder matrix. Finally, the performance of transgenic mouse bladder transplants during matrix-driven bladder regeneration will elucidate the role of growth factors in bladder regeneration. The long-term objective of this research is to develop effective therapeutic strategies for treating bladder dysfunction based upon stromal-epithelial interactions.